Enhanced transport of polyelectrolyte stabilized nanoscale zero-valent iron (nZVI) in porous media

Laboratory experiments including column and batch sedimentation studies were conducted to investigate the transport of nanoscale zero-valent iron (nZVI) particles stabilized by three polyelectrolytes: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A), poly(acrylic acid) (PAA) and soy proteins. Results of the continuous packed column study suggest that the both PV3A and PAA can increase nZVI mobility by reducing particle size and generating negatively charged surfaces of nZVI. PV3A stabilized nZVI has the best transport performance among the three materials. It was found that approximately 100% of nZVI flowed through the column. Retardation of nZVI is observed in all tests. Due to the large surface area of nZVI, large amounts of polyelectrolytes are often needed. For example, soy proteins exhibited an excellent stabilization capability only at the dose over 30% of nZVI mass. Approximately 57% of nZVI remained in the column when nZVI was stabilized with PAA at the dosage of 50%. Results suggest that nZVI may be prepared with tunable travel distance to form an iron reactive zone for the in situ remediation.